This proposal requests continued funding for five years for a randomized trial of breast self examination (BSE), currently underway in 520 factories of the Shanghai Textile Industry Bureau (China). The purpose of the study is to determine whether the regular practice of BSE will reduce mortality from breast cancer. Nearly 300,000 current and retired female workers between the ages of 30 and 64 have been randomly allocated by factory to an intervention or control group. Baseline interview data are being collected from all study participants, and women in the intervention group are receiving initial BSE instruction and reinforcement during the current funding period. Under the renewal, intensive and repeated instruction in BSE will be continued, and additional motivation provided to practice BSE correctly on a regular basis. In addition, compliance with requests to practice BSE and competency in BSE performance will be continuously monitored. All women will be followed for 10 years from initial inclusion in the study for the occurrence of breast cancer and mortality from breast cancer and all other causes using multiple active and passive reporting systems. Initial follow-up procedures have been implemented during the current funding period; additional procedures will be implemented during the renewal. This study has a power of approximately 80% to detect a reduction in breast cancer mortality of about 30%. Interim analyses will be performed during the fifth year of this proposed grant period (mean follow-up of six years, 1.8 million women-years), and the trial will be terminated at that time if a significant reduction in breast cancer mortality is observed; otherwise, a final continuation application will be submitted. This trial is being conducted under virtually optimal conditions and experience to date suggests that successful completion of the study is highly likely. The results will provide an estimate of the upper limit of the beneficial effects that can reasonably be expected of BSE in most situations, and will therefore provide information needed to estimate the potential impact that BSE could have in reducing mortality from breast cancer in the United States.